You can get a tarball for it from http://wiki.maemo.org/Mer/Releases/0.16 . The 770 version is at the very bottom of the page. Most browsers make a peculiar twitch upwards when you go that far down, concealing the link almost immediately. You can prevent that by placing your cursor over the link in the brief time when it is visible.

The installation instructions are all right in general, although I didn't follow them exactly. I don't use wget or the latest bootmenu app (wget takes up too much space in the 770's internal flash when you have 2008HE installed). Instead, I used a PC to download the tarball into the MMC in a card reader. For the bootmenu, I'm still happy with Fanoush's original initfs_flasher, using vi to edit the bootmenu.conf.

[EDIT: I might not be remembering correctly how I downloaded. I might possibly have downloaded to Shared Folders on the Windows PC and copied it from there to the MMC in the 770 via wifi. Or I might have copied it via a USB thumb drive - the 770 is flashed to persistent host mode, so that it behaves like a computer instead of a $7 card reader.]

There is one error in the instructions. I believe that you ought to cd out of /mnt/mer before unmounting it.

It turns out that you have to untar the tarball on the 770 itself. When I did it on the PC (with MMC in the card reader), mer would not boot on the 770.

I assume that gtar will work on the 770. I am still using the old explosive osso-tar that has disappeared from the repositories.

Good luck with mer. I can't honestly promise that it will be much fun. It does fill a specific need though, if you urgently want to connect your 770 to wifi.